Secret-Gate

Secret Gate

Overview

Secret Gate is a self-hostable, ephemeral messaging engine designed for users seeking an anonymous inbox without giving server access to their messages. By leveraging the power of the Web Crypto API, it enables users to generate a secure link for message delivery, ensuring that only the sender and intended recipient can access the information. The server is never privy to the plaintext content, as it only stores ciphertext which it cannot decrypt.

This system operates without the need for signup, email, or phone verification. Messaging is facilitated through a unique keypair, a secure password, and a simple link. When a message or link reaches its expiration, it is automatically deleted from the database, thus enforcing data integrity without relying on user trust.

Developed with a focus on simplicity and transparency, Secret Gate consists of approximately ten PHP files and requires no dependencies or frameworks, allowing users to deploy it effortlessly on standard LAMP stacks.

Key Features

• True Zero-Knowledge Encryption: Implements hybrid RSA-OAEP (2048-bit) and AES-256-GCM encryption techniques, handled entirely client-side using window.crypto.subtle, ensuring that the server cannot access message content.
• Server-Side Private Key, Zero Exposure: Each message link includes a private key wrapped with an AES-256-GCM encryption key derived from a password, which is stored securely in the browser's IndexedDB.
• Minimalist Architecture: Free from bloat; no external frameworks like Laravel or Symfony, resulting in concise and auditable code.
• Ephemeral Messaging: Messages are designed for temporary use, with strict time-to-live (TTL) management enforced at the database and cache levels.
• Robust Security Protocols: Incorporates Argon2id for password hashing, stringent CSRF protection on state-altering requests, and prepared statements globally to prevent SQL injection.
• Privacy by Default: The system does not collect any personally identifiable information (PII), ensuring that what is not collected cannot be compromised.
• Abuse-Resistant Measures: Utilizes Redis for rate limiting, IP blacklisting, and other techniques to mitigate spam and misuse.
• Flexible Deployment: Can be run on any standard Apache + PHP-FPM + MySQL configuration with no additional containerization requirements.

Architecture & Encryption Flow

Secret Gate implements a hybrid encryption model: an RSA-OAEP keypair for inbox creation and unique AES-256-GCM keys for each message, striking a balance between secure key management and efficient encryption.

┌─────────────────────────────────────────────────────────────────────────────┐
│                         1. INBOX CREATION (Owner)                           │
│   ...    // workflow description    ...                                       │
└─────────────────────────────────────────────────────────────────────────────┘

This meticulous architecture allows anonymous senders to securely encrypt messages using only the public key, circumventing the need for shared secrets or prior interactions.

Security Features Overview

Secret Gate adheres to rigorous security protocols at various layers:

• Message Integrity: Content remains unrevealed to the server through client-side encryption (AES-256-GCM).
• Private Key Safety: Private keys are securely generated and managed only within the user's browser environment, mitigating the risk of exposure.
• Data Minimization: The system collects no personal data, ensuring a robust privacy posture.

By focusing on minimal complexity and maximal security, Secret Gate offers a comprehensive solution for ephemeral and anonymous messaging requirements, making it an ideal choice for those prioritizing privacy in their communications.